1. Field of the Invention
This invention relates to heat insulated hoses and, more particularly, to a flexible heat insulated hose suited particularly for heat insulated ducts for transporting air conditioning gases, with which piping can be laid in a freely bendable fashion.
2. Description of the Prior Art
The heat insulated hoses of this kind are typically applied for air-conditioning duct hoses, as used in a high density heat insulated house shown in FIG. 13. The high density heat insulated house refers to a house in which heat loss occurring through the wall, ceiling, floor, etc. is decreased in order to save the energy required for air conditioning with the in-door temperature and humidity kept stable, providing for comfortable residence environment. In such a house, however, natural ventilation is difficult to implement leading to problems involving air contamination, dew condensation, gathering mold, etc.
To avoid the problems, in this type of a house is adopted an air ventilating or conditioning system which includes local ventilation in kitchen, bath room, etc. to implement air intake and discharge. With such a system, flexible ducts are laid through narrow spaces, such as in-ceiling space and first-to-second floor space, connecting between air blowers, fans, inlet/exit ports of air intake/discharge devices such as air-conditioners, air discharge/suction ports leading to rooms, in order to introduce outdoor air into the room interior through the duct and expel in-room air to the outside through the duct.
The duct used in such an application requires a flexible, elongate hose to facilitate piping work. The hose must be light in weight, easy to handle and low in fluid pressure loss with smoothened inner surface.
Further, the duct experiences significant temperature difference between the inside and outside thereof. Measures have to be taken to prevent dew from condensing on the outer surface of the duct. In this respect, heat insulatability is at least required for the duct. Moreover, there is a fear that noise due to the air intake/discharge device propagate into the room via the duct acting as a sound passage. Due to this, sound absorbability has to be given to the duct. That is, the heat insulated hose to which the invention is directed preferably has both heat insulatability and sound absorbability.
In FIG. 13, an elongate flexible duct hose 3 is used to connect between an intake port 1 leading to an air conditioner or the like and an exit port 2 leading to a room interior. Also connection is made by an elongate flexible duct between a suction port 4a and suction box 4b leading to the room requiring air ventilation and discharge port 5 leading to the outside of the room. Incidentally, the duct hose 3 is laid through a heat-pump type heat-exchanging air conditioning in-door unit 6 and a branch pipe 7. In a house as in FIG. 13, the room temperature and humidity are controlled by introducing cool or warm air through the exit port 2 into the room interior. At the same time, contaminated air is sucked through the suction port 4a or suction box 4b and discharged through the discharge port 5.
A first prior art of a heat insulated hose suitably applicable for the above type of the flexible duct hose is disclosed, for example, in Japanese Laying-Open No. H5-187594 [F16L 59/153, 11/10] laid open to public on Jul. 27, 1993. The heat insulated hose in the first prior art is structured by an inner layer formed by helically wining a non-rigid synthetic tape, and an outer layer formed thereon by helically winding a rigid resin rigid synthetic tape over an outer periphery of the foamed resin tape.
In this prior art heat insulated hose, the non-rigid resin tapes of the inner and outer layers are required as materials for the hose, separately from the foamed resin tape for the insulation layer. There is a difficulty in reducing the wall thickness of these non-rigid resin tapes to an extreme extent, thus imposing limitation to the light-weightening as desired in handling the hose.
Further, a plurality of tapes, including an inner-layer non-rigid resin tape, insulation-layer foamed resin tape and outer-layer non-rigid resin tape, have to be helically wound by laminating over one another at a same pitch to form a hose. Accordingly, there requires an equipment to induce the respective tapes onto an axis of hose forming. This, however, requires complicated pitch-adjusting operations as well as troublesome management on inventories of the various tapes.
Also, a second prior art is disclosed, for example, in Japanese Patent Laying-Open No. H9-89357 [F24F 13/02 F16L 55/02] laid open to public on Apr. 4, 1997. The heat-insulated sound-absorbing duct in this second prior art has an inner layer, an open-cell foamed resin layer, an intermediate sheet layer, a closed-cell foamed resin layer and an outermost layer, which are separately layered in order from the inner side.
In this second prior art heat-insulated sound-absorbing duct, a multiplicity of layer-foaming strips have to be helically wound by laminating in order at a same pitch, in addition to the fibrous and resin-reinforcing strips as inner-layer forming materials. This therefore requires an equipment to induce the various strips onto a hose forming axis. Further, there encounters troublesomeness in pitch adjusting operations and management on inventories for the various strip materials. In addition, there is a limitation against the realization of duct weigh reduction.